1. Field of the Invention
The present invention provides generally a concrete or cement dispersant and a method of using the dispersant. Specifically, the present invention provides a cement or concrete dispersant having a covalently bonded sulfur moiety.
2. Discussion of Related Art
Workability and durability of cement and concrete (hereinafter “concrete”) are important parameters for concrete structures. Dispersants have been used to improve both workability and durability of the cement used to make the concrete structures. Dispersants are also known as fluidity modifiers or slump modifiers and are introduced into freshly mixed concrete to improve the workability of the concrete while reducing the amount of water needed for purposes of transportation, pouring and placing the concrete.
Current dispersants include naphthalene-based dispersants, aminosulfonic acid based dispersants, and polycarboxylic acid based dispersants. These dispersants improve the slump properties or flow characteristics of the concrete. Slump loss is still a persistent problem encounter ed in the field. A delay in the delivery of the concrete to a worksite or a variation in ambient temperature can negatively impact the concrete and decrease the slump. Any advantages to using the dispersant may be lost.
Carboxylate salts can be formed in several ways. Non-polar, polar and ionic bonding types are available for functional groups to attach to a carboxylate group to form a salt. The bonding type strongly affects such properties as the water solubility of the resultant molecule. Further, the choice of cation affects such properties as the water solubility. As noted above, ionic and non-ionic polymers have been used as concrete dispersants. As used herein ionic refers to radicals having separated charges, and includes both anionic polymers and to a lesser extent cationic polymers. Non-ionic, as used herein, refers to hydrogen bonding, or bonding via Van der Waals forces. Accordingly, anionic and non-ionic polymers conventionally used as dispersants do not have covalently bonded sulfate moieties.
While current dispersants improve the slump properties of the concrete, often the amount of dispersant necessary to achieve a predetermined level or degree of slump is greater than is desirable. There still exists a need for a dispersant that improves slump properties of freshly mixed concrete.